ext3 and ext4 (for quite some time) with default mount options don't
need fsync() to ensure safety of replace-by-rename. Stop doing that for
these filesystems.
Note: this patch also impacts ext2, which is probably not safe, but I
don't know of any way to check ext2. vs the others because they all have
the same magic numbers (short of opening /proc/mount).
This patch assumes that if BTRFS_SUPER_MAGIC is defined then so will be
EXT3_SUPER_MAGIC.
https://bugzilla.gnome.org/show_bug.cgi?id=701560
/* On Linux, on btrfs, skip the fsync since rename-over-existing is
* guaranteed to be atomic and this is the only case in which we
* would fsync() anyway.
+ *
+ * ext3 and ext4 are also safe in this respect under the default
+ * mount options (and if someone picks non-default options to
+ * improve their performance at the cost of reliability, who are we
+ * to argue?)
+ *
+ * Note: EXT[234]_SUPER_MAGIC are equal.
*/
- if (fstatfs (fd, &buf) == 0 && buf.f_type == BTRFS_SUPER_MAGIC)
+ if (fstatfs (fd, &buf) == 0 && (buf.f_type == BTRFS_SUPER_MAGIC || buf.f_type == EXT3_SUPER_MAGIC))
goto no_fsync;
}
#endif